CVE-2026-31409 (GCVE-0-2026-31409)
Vulnerability from cvelistv5
Published
2026-04-06 07:38
Modified
2026-08-05 12:22
Severity ?
8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ksmbd: unset conn->binding on failed binding request When a multichannel SMB2_SESSION_SETUP request with SMB2_SESSION_REQ_FLAG_BINDING fails ksmbd sets conn->binding = true but never clears it on the error path. This leaves the connection in a binding state where all subsequent ksmbd_session_lookup_all() calls fall back to the global sessions table. This fix it by clearing conn->binding = false in the error path.
References
Impacted products
Vendor Product Version
Linux Linux Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
Version: f5a544e3bab78142207e0242d22442db85ba1eff
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{
  "containers": {
    "cna": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/smb/server/smb2pdu.c"
          ],
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        {
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          "product": "Linux",
          "programFiles": [
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
              "version": "5.15.209",
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            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.167",
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            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.130",
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            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.78",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.20",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.19.*",
              "status": "unaffected",
              "version": "6.19.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.0",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.209",
                  "versionStartIncluding": "5.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: unset conn-\u003ebinding on failed binding request\n\nWhen a multichannel SMB2_SESSION_SETUP request with\nSMB2_SESSION_REQ_FLAG_BINDING fails ksmbd sets conn-\u003ebinding = true\nbut never clears it on the error path. This leaves the connection in\na binding state where all subsequent ksmbd_session_lookup_all() calls\nfall back to the global sessions table. This fix it by clearing\nconn-\u003ebinding = false in the error path."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - ksmbd processes SMB2 SESSION_SETUP and later SMB commands from remote peers over TCP/445 or SMB Direct. The vulnerable state is reachable through network SMB packets.\nAC:L - An attacker can deterministically create valid SMB3 sessions, send a malformed or failing binding SESSION_SETUP, and then issue further requests on the same connection. There is no race or condition outside the attacker\u0027s control beyond multichannel being enabled on the affected server.\nPR:L - The binding path requires an existing valid non-guest SMB session, which a basic authenticated SMB user can create. It does not require local system privileges or administrator/root access.\nUI:N - No victim action is needed after the server is running; exploitation is performed by sending SMB protocol messages. The attacker controls the network requests directly.\nS:U - The vulnerability breaks ksmbd\u0027s own session/channel authorization model but does not cross a separate security authority such as a VM, hypervisor, or sandbox boundary. The affected resources remain within the SMB server/kernel security scope.\nC:H - Leaving conn-\u003ebinding set lets subsequent session lookups fall back to the global session table, allowing a low-privileged SMB user to act through other valid sessions by session ID. This can expose arbitrary files and data accessible to hijacked SMB sessions.\nI:H - The same session confusion can allow creating tree connections and issuing file operations as another SMB user/session. That can modify or delete data with the victim session\u0027s privileges.\nA:H - The attacker can issue operations such as LOGOFF, tree disconnects, file closes, deletes, or repeated disruptive requests against other active sessions. This can cause complete availability loss for affected SMB sessions and their open files."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:22:18.697Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/7e8b270813079c785696bce8802a3f920665c88c"
        },
        {
          "url": "https://git.kernel.org/stable/c/d073870dab8f6dadced81d13d273ff0b21cb7f4e"
        },
        {
          "url": "https://git.kernel.org/stable/c/6ebef4a220a1ebe345de899ebb9ae394206fe921"
        },
        {
          "url": "https://git.kernel.org/stable/c/89afe5e2dbea6e9d8e5f11324149d06fa3a4efca"
        },
        {
          "url": "https://git.kernel.org/stable/c/9feb2d1bf86d9e5e66b8565f37f8d3a7d281a772"
        },
        {
          "url": "https://git.kernel.org/stable/c/6260fc85ed1298a71d24a75d01f8b2e56d489a60"
        },
        {
          "url": "https://git.kernel.org/stable/c/282343cf8a4a5a3603b1cb0e17a7083e4a593b03"
        }
      ],
      "title": "ksmbd: unset conn-\u003ebinding on failed binding request",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31409",
    "datePublished": "2026-04-06T07:38:21.223Z",
    "dateReserved": "2026-03-09T15:48:24.087Z",
    "dateUpdated": "2026-08-05T12:22:18.697Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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